micro inquizitive ch.16
A single B cell has approximately 50,000 B-cell receptors. How many distinct epitopes is this cell capable of recognizing?
1 epitope(s)
T or F: Each B cell is capable of recognizing and producing antibody to multiple antigens of a single pathogen.
False
The killing of infected cells by cytotoxic T cells resembles the process of killing by natural killer cells. How do the two processes differ?
NK cells do not recognize specific antigen.
Which of the following is an example of a hapten? a. penicillin b. peptidoglycan c. interferon d. a conformational epitope
a. penicillin
IgG is able to bind to antigens on the surface of a pathogen. Once bound, the Fc region of the antibody is exposed and can interact with phagocytes, increasing the likelihood the pathogen will be engulfed and destroyed. What term describes the process of IgG binding to the pathogen?
opsonization
Release of cytokines from immune cells stimulates other cells to release these molecules as well, which can lead to an over-amplification of these signals known as a cytokine storm. Some proteins (including known bacterial toxins) can trigger this response by directly binding to the outside of T-cell receptors without being recognized or processed as antigens. What is the name of these proteins?
superantigens
T cells are subdivided into many types, each of which has a particular function in the response to a pathogen. Match the T-cell type to its primary role. T-cell type: -TH2 -TC -TH17 -Treg -TH1 Primary role: -B-cell activation -activate cytotoxic T cells -anti-inflammatory -destroy infected or cancerous body cells -pro-inflammatory
-TH2 - B-cell activation -TC - destroy infected or cancerous body cells -TH17 - pro-inflammatory -Treg - anti-inflammatory -TH1 - activate cytotoxic T cells
How are T-cell receptors similar to B-cell receptors?
Both bind specific antigens.
T or F: Isotype switching occurs only from IgM to IgG.
False
T or F: Killing of infected cells by cytotoxic T cells is beneficial and not harmful to the host.
False
Associate the following items with either major histocompatibility complex class I or major histocompatibility complex class II. -found only on APCs (dendritic, macrophage, and B cell) -recognized by CD8 T cells -recognized by CD4 T cells -found on all nucleated body cells -presents antigen produced within APCs -presents antigen phagocytosed by APCs
MHC I: -recognized by CD8 T cells -found on all nucleated body cells -presents antigen produced within APCs MHC II: -found only on APCs (dendritic, macrophage, and B cell) -recognized by CD4 T cells -presents antigen phagocytosed by APCs
T cells must be educated in the thymus to avoid damaging self-recognition. In this process, what is the fate of T cells that weakly recognize self MHC?
These cells leave the thymus and move to secondary lymphoid tissues.
B cells must be activated in order to begin clonal expansion into populations of plasma cells that produce antibody. This process may be T-cell independent or T-cell dependent. In T-cell-dependent activation, B cells must first bind to an antigen that matches their existing B-cell receptors' _____________ regions. The B-cell receptor is a structure composed of an _____________ and two additional membrane proteins. The bound antigen is _____________ by the B cell and then processed and attached to _____________, which is re-displayed on the cell surface. This process makes the B cell its own ____________. A ____________ is then able to bind the antigen display complex and activate the B cell, allowing clonal proliferation.
variable, antibody, endocytosed, MHC II, antigen-presenting cell, helper T cell
Match the cell type to its description. Type: -helper T cell -memory B cell -plasma B cell -cytotoxic T cell Description: -kills infected host cells displaying antigen -produces and secretes antibodies -activates other adaptive immune cells -rapidly produces new antibody-secreting cells following re-exposure to antigen
-helper T cell - activates other adaptive immune cells -memory B cell - rapidly produces new antibody-secreting cells following re-exposure to antigen -plasma B cell - produces and secretes antibodies -cytotoxic T cell - kills infected host cells displaying antigen
A cytotoxic T cell with a TCR specific to virus X antigen is present in a person infected with virus X. What must occur for the cytotoxic T cell to help resolve the infection in this person? Place the steps in the correct order.
1. An APC from an infected site presents virus X antigen on MHC I. 2. Tc cell binds MHC I and the TCR binds virus X antigen. 3. Tc cell receives IL-2 from activated TH1 cell. 4. Tc cell is activated. 5. Tc cell travels to site of infection.
A primary antibody response is initiated following exposure to a pathogen for the first time. Order the primary antibody response below.
1. Foreign antigen binds B cell with appropriate antibody. 2. B cells become activated and differentiate into plasma and memory cells. 3. Low-affinity IgM is produced and secreted into serum 4. Isotype switching occurs. 5. Large quantities of IgG are produced and secreted into serum. 6. Plasma cells die.
Which is an example of cross-protection? a. Antibodies to cowpox can provide some protection against smallpox. b. E. coli strains are characterized by their varied flagellar antigens. c. Infection by one rhinovirus provides protection against infection by most other strains. d. The body produces both cellular and humoral immune responses to a single pathogen.
a. Antibodies to cowpox can provide some protection against smallpox.
Mothers can naturally, passively provide protection against pathogens to their infants by giving them pre-formed antibodies that are able to prevent some pathogens from adhering to the infant's intestinal cells and infecting. Which antibody type would be associated with this protection? a. IgA b. IgG c. IgE d. IgM
a. IgA
Which are true of regulatory T cells? a. inhibit T cells that should have been eliminated in the thymus but were not b. possess CD4 c. weakly recognize self antigens d. regulate the activation of B cells and helper T cells
a. inhibit T cells that should have been eliminated in the thymus but were not b. possess CD4
What term describes the strength of the binding between an antibody and its epitope?
affinity
What term describes the degree of immune-response induction that an antigen can produce?
antigenicity
Memory B cells require an activation signal in addition to specific antigen binding in order to produce new plasma cells. What is the second, activating signal?
secreted IL-4 and IL-6 from activated helper T cells
Following exposure to a pathogen, antibodies are produced as a part of the adaptive immune response. Place the steps of this response in the order that they generally occur.
1. Pathogen enters the body. 2. Antigen-presenting cell engulfs pathogen. 3. Antigen-presenting cell presents antigen to helper T cell. 4. Helper T cell becomes activated. 5. Helper T cell activates B cell which has previously bound the same antigen. 6. B cell clonally expands. 7. Plasma B cells produce antibody.
T or F: The constant region of antibodies' heavy chains has the same amino acid sequence in all classes of immunoglobulin.
False
The power of adaptive immunity can be used to prevent disease. By exposing people to certain antigens before they come into contact with the associated pathogens, the adaptive immune response can respond fully before the pathogen has a chance to replicate and cause illness. The process of exposing a person to _____________ in order to allow an adaptive immune response that prevents disease is _____________. Most _____________, the materials administered to the person in this process, are currently composed of weakened or _____________ microorganisms, killed pathogens, or inactivated protein ____________.
antigens, vaccination, vaccines, attenuated, toxins
Which steps contribute to the generation of antibody diversity? a. enzymes that reshape receptors b. generation of different codons c. random mutations d. rearrangement of genes in the genomes of B cells
b. generation of different codons c. random mutations d. rearrangement of genes in the genomes of B cells
Which is most likely to be a potential antigen? a. a single amino acid b. a bacterial capsule c. a bacterial exotoxin d. a nucleotide
c. a bacterial exotoxin
T-cell-independent activation of B cells is associated with which of the following? a. helper T cells b. soluble antigens not attached to a microbe c. complexing of antigen to MHC II d. capping or cross-linking of multiple B-cell receptors
d. capping or cross-linking of multiple B-cell receptors
The adaptive immune response allows the body to recognize specific pathogens it has encountered previously, thereby providing an efficient and targeted response to that pathogen when it is encountered again. The adaptive immune response is divided into two branches. The first is ____________ immunity, in which antibodies are produced that bind to ____________ associated with the foreign cell. In the second branch, ____________ immunity, _____________ recognize foreign cell structures and may either destroy infected ____________ cells or help activate ____________, which can then generate plasma cells that produce _____________.
humoral, antigens, cellular, T cells, host, B cells, antibodies
Match the characteristic to the class of antibody with which it is primarily associated. More than one characteristic may be associated with an antibody class. Class of antibody: -IgE -IgM -IgG -IgA -IgD Characteristics: -commonly found as a dimer -first antibody produced in the initial adaptive immune response -secreted across mucosal surfaces -transmitted across the placenta from mother to fetus -most abundant antibody in blood -associated with the degranulation of mast cells and allergy -commonly found as five monomers joined by a J-chain -found at low levels in blood but is abundant on the surface of B cells
IgE -associated with the degranulation of mast cells and allergy IgM -first antibody produced in the initial adaptive immune response -commonly found as five monomers joined by a J-chain IgG -transmitted across the placenta from mother to fetus -most abundant antibody in blood IgA -commonly found as a dimer -secreted across mucosal surfaces IgD -found at low levels in blood but is abundant on the surface of B cells
T or F: Antigenicity of an epitope is dependent on its shape. Denaturing proteins generally removes the conformational epitope.
True
T or F: Suppose that a B cell is activated by two signals. The first signal is capping. The second signal is a TLR on the B cell interacting with a PAMP. Given these two signals, the B cell will produce only IgM and no further class switching will occur.
True
T or F: Though each antibody is specific to one antigen, highly similar antigens may be recognized by the same antibody. Because of this, some foreign antigens that resemble self antigens are "ignored" by the immune system in order to prevent damage to the body's own cells.
True
Which of the following statements regarding adaptive immunity are true? a. Microbial pathogens are composed of many antigens. b. Each antigen is composed of a single epitope. c. Antibodies are a component of the cellular immune response. d. Antigens elicit the formation of specific antibodies.
a. Microbial pathogens are composed of many antigens. d. Antigens elicit the formation of specific antibodies.
Which of these techniques might microbes use to successfully evade an immune response mounted against them? a. inhibit production of pro-inflammatory cytokines b. induce production of MHC complexes c. induce production of anti-inflammatory cytokines d. trigger apoptosis of immune cells
a. inhibit production of pro-inflammatory cytokines c. induce production of anti-inflammatory cytokines d. trigger apoptosis of immune cells
Different immune responses are more appropriate than others to provide protection from particular pathogen types. Fill in the blanks to accurately describe this regulation. Extracellular pathogens are most effectively targeted by _____________ immunity and the production of antibodies, while intracellular pathogens cannot be reached by antibodies and must therefore be targeted by the ______________ immune response. Direction of this response to a particular pathogen is largely governed by the ratio of T-cell types produced and the _____________ these cells secrete locally. More subtle control of this response may also be achieved. For example, TH2 cells directly stimulate B cells to class switch, producing immunoglobulin isotype _____________ , which is useful in targeting _____________.
humoral, cellular, cytokines, IgE, parasitic worms
Fill in the blanks below to create a correct statement regarding antibody diversity. Amino acid sequence differences distinguish five classes of antibodies in humans: IgG, IgA, IgM, IgE and IgD, each of which represents a distinct ____________. While all humans possess IgD, your IgD ____________ differs in several small ways from those of others, including members of your own family. Within your own body, you make many IgD monomers that are specific to antigens from many foreign sources; these IgD immunoglobulins differ at the ____________ level.
isotype, allotype, idiotype
Different antigens interact with the adaptive immune system in different ways, with several features influencing how great the immune response will be to a given antigen. Nucleic acids and lipids are weaker antigens than ____________ in part because they are made of relatively uniform repeating units and are flexible. Size is also a factor, with _____________ antigens being more readily presented on MHC than ____________ antigens. Each antigen has a different ____________ dose that will produce the optimal immune response. A lower dose will activate few B cells, while an excessive dose produces a tolerance response called ____________ in which antibodies are not produced following subsequent exposures. This response helps prevent the body from recognizing its own "self" antigens, which are generally abundant.
proteins, larger, smaller, threshold, anergy
